1. Field of the Invention
The present invention relates to vertical deposition masks and their fabrication, and, more particularly, to a method and apparatus for fabricating the vertical deposition mask such that the mask is prevented from drooping.
2. Discussion of the Related Art
In general, a mask is used for depositing a layer having a predetermined pattern when fabricating a light emitting display. That is, when a layer such as an organic layer is deposited, a layer having a pattern corresponding to apertures is formed on a substrate using the mask having apertures in a specific pattern.
The mask is formed of a metal having predetermined strength in order to maintain the shape of the apertures of the specific pattern, and the deposition process is performed after horizontally positioning the substrate on which the mask is provided.
However, the center of the mask can droop due to the weight of the mask and generate an error in the pattern of the layer deposited on the substrate during the deposition process.
Such a problem becomes severe when a large area substrate is deposited since, as the size of the substrate on which deposition is performed increases, the size of the mask corresponding to the size of the substrate also increases so that the center of the mask remarkably droops due to the weight of the mask.
FIG. 1 is a perspective view illustrating a conventionally fabricated mask sheet and a mask to which a mask frame is welded. FIG. 2 illustrates that the drooping of the mask of FIG. 1.
Referring to FIGS. 1 and 2, a mask 10 includes a mask sheet 11 in which apertures of a predetermined pattern are formed and a mask frame 13 for fixing the mask sheet 11.
The mask 10 is fabricated by welding the mask sheet 11 and the mask frame 13 using a mask fabricating apparatus.
That is, the mask fabricating apparatus fixes the edge of the mask sheet 11 by a clamp (not shown), attaches the mask sheet 11 fixed in place by the clamp to the mask frame 13, and the attached region is welded to fabricate the mask.
In the conventional art, the mask fabricating apparatus performs welding after horizontally positioning the mask sheet 11 and the mask frame 13. However, the fabricated mask 10 can droop in a plane direction due to the load of the mask sheet 11 as illustrated in FIG. 2.
Therefore, a welding line between the mask sheet 11 and the mask frame 13 does not form a straight line 14 but forms a curved line 15. As a result, the positions of the apertures 12 formed in the mask sheet 11 are not formed as desired.
As such, a thin film pattern is not uniformly formed on the substrate using the mask 10 and the position of the thin film formed on the substrate is not formed in the desired position on the substrate.